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Balun vs. UNUN vs. Transformer

Jun 20th 2019, 10:33


Joined: May 1st 2019, 20:27
Total Topics: 0
Total Posts: 0
I am a "newbe". My rig is an Icom 7300 using a 4 band Diapole antenna.
I have been considering home brewing my next antenna. I have read MANY articales and have watched numerous videos on how to build Baluns and unun. I believe I can do that successfully.
My question regards the purpose and use of transformers. Being a new ham, I would like a simple answer.
Jun 20th 2019, 12:46


Super Moderator

Joined: Apr 4th 1998, 00:00
Total Topics: 0
Total Posts: 0
A transformer is used to match impedances. Many antennas do not present a resistive 50 ohm impedance so the use of the proper transformer is one technique for lowering the SWR.

A balun stops the current on the outside of the shield of a coaxial cable. The skin effect isolates the inside of the shield from the outside of the shield. The current on the outside of the shield is often undesired, so removing it will improve antenna performance.

An unun is merely a transformer. It may combine currents from the outside of the shield and the inside of the shield. In some cases, this can significantly degrade reception.

Zak W1VT
ARRL Senior Lab Engineer

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